Blowout preventer

ABSTRACT

An annular blowout preventer comprising a housing having a bore through it and an annular recess extending outwardly from the bore, and a packer within the recess including an annulus of deformable material having a bore aligned with the housing bore and a circular series of rigid inserts extending therethrough from one end to the other. A sealing surface on an end portion of the annulus engages the oppositely facing end surface of the recess, and there are radially movable parts about the outer side of the annulus for constricting the packer to urge its bore into position to seal about a member in the bore of the housing or upon itself when the bore is empty. The packer is symmetrical end-for-end so that it may be disposed with either end up, and each of the rigid inserts includes a rib which has opposite sides lying generally in planes of least strain of the deformable material of the annulus during radial movement of the inserts upon constriction of the packer.

United States Patent [72] Inventor Marvin R. Jones Houston, Tex.

[21 Appl. No. 765,066

[22] Filed Oct. 4, 1968 [45] Patented Mar. 30, 1971 [73] AssigneeCameron Iron Works. Inc.

Houston, Tex.

ousing having a bore through it and ing outwardly from the bore, eludingan annulus of deformable material having a bore [54] BLOWOUT PREVENTElR20 Claims, 12 Drawing lFigs.

aligned with the housing bore and a circular series of rigid insertsextending therethrough from one end to the other. A gages the l .l s 2 LC S U n 5 2 /5, 27 /1 77/235 sealing surface on an end portion of theannulus en Int.

s, and there are radiof the annulus for conoppositely facing end surfaceof the reces ally movable parts about the outer side 50FieldofSearch....".3:iI::Ziliiiiiidiiiiit 83 stricting the packer tourge its bore into position to seal about g or upon itself when the 235a member in the bore of the housin bore is empty. The packer issymmetrical end-for-end so that [56] References Cited it may be disposedwith either end up, and each of the rigid in- UNITED STATES PATENTSserts includes a rib which has opposite sides lying generally in1,708,261 4/1929 Crowell et planes ofleast strain of the deformablematerial ofthe annulus 251/] during radial movement of the inserts uponconstriction of the 277/73 packer.

1,963,683 6/1934 Shaffer......... 2,609,836 9/1952 Patented I March 30,1971 5 Sheets-Sheet 1 Marv/r2 Jone;

Patented .March 30, 1971 5 Sheets-Sheet 2 Marv/n l7. c/anes INVEN'I'OR.

ATTORA/E VJ Patented March 30, 1971 3,572,628

5 Sheets-Sheet 5 rv l7 /P. (/6093 INVENTOR.

Patented March 30, 1971 5 Sheets-Sheet 4 Mar F. J60 e J INVEN'I'UR.

BLOWOUT PREVENTER This invention relates generally to blowout preventersand, more particularly, to improvements in annular blowout preventers.

As well known in the art, a blowout preventer controls the pressurewithin an oil or gas well during drilling and completion of the well. Itcomprises a housing adapted to be connected above the head of the wellwith its bore aligned with the well bore, and one or more packingelements carried within a recess in the bore. The packing element orelements are adapted to be moved inwardly for closing about a pipe orother member in the bore or for closing the entire bore when it isempty.

- An annular blowout preventer has a single packer comprising an annulusof rubber whose bore is adapted to be radially constricted. In one suchannularblowout preventer which is shown and described in U.S. Pat. No.2,609,836, the packer comprises a massive annulus of rubber having rigidinserts molded into it for containing it during constriction. Theseinserts extend from one end to the other of the annulus and compriselongitudinally extending ribs having flanges at their opposite endswhich move radially inwardly as the bore is constricted.

The outer side of the annulus is conically shaped for seating upon asimilarly shaped upper surface of an annular piston which is verticallyreciprocable within the housing. As the piston is moved upwardly, itsface slides over the outer side of the annulus to seal thereabout andmove it inwardly in order to constrict the packer. This constructionrequires a large housing, and in particular, one high enough to permitthe required vertical stroke of the piston; despite the fact thatheadroom is often at a premium in the environment in which blowoutpreventers are used. Also, since the piston must slide over asubstantial portion of theouter side of the annulus, it requiresconsiderable operating force, which adds to the size and cost of thepreventer. Still further, the strain induced in the annulus as it isurged inwardly breaks its bond to the rigid inserts, and, as a result,the packer may fail.

An object of this invention is to provide an annular blowout preventerwhich is lighter and smaller and, particularly, of less. height than theannular blowout preventer above described.

Another object is to provide an annular blowout preventer which haslower operating pressure. requirements than the blowout preventer abovedescribed, and in which the packer may be constricted by piston operatedparts with greatly reduced sliding thereover.

A further object is to provide a blowout preventer of the type describedin one or both of the foregoing objects in which the packet constrictingparts are easily accessible for replacement or repair.

Still another object is to provide an annular blowout preventer in whichthe packer comprises an annulus provided with rigid inserts in such amanner as to reduce the likelihood of breaking their bond withtheannulus.

These and other objects are accomplished, in accordance an annularblowout preventer in which there are parts within an annular recess inthe housing and about'the outer side of the packer which are movableradially inwardly against the outer sideof the packer to constrict thepackerbore. Rigid inserts extend through the annulus from one end to theother, and a sealing surface surrounding the bow on at least one end ofthe annulus initially engages an oppositely facing end of the housingrecess. This sealing surface preferably comprises a protuberance whichis urged into-tight engagement with the end of the recess as the packeris moved'to constricted position. Preferably, such a sealing surface isprovided at both ends of the annulus so that the packer may be installedwith either end .up.

Inasmuch as the packer constricting parts move radially, they require nomore height within .the housing than does the packer itself.Furthermore, these constricting parts are reciprocated by pistons whichhave short strokes, so that the housing need not be particularly largein diameter. Consequently, the housing of this blowout preventer may besmaller than that described in the above-mentioned US. patent. Stillfurther, since they move in the same direction, the only sliding whichtakes place between the annulus and the constricting parts is that dueto the small relative circumferential displacement between them.

In accordance with another novel aspect of the invention, the cylindersreceiving the pistons extend radially into the housing from its outerside, and a ring is disposable over the outer side of the housing toform a common cover over the outer ends of all of the cylinders. Thus,hydraulic fluid may be introduced through a common line into the spacebetween the outer ends of the pistons and the inner side of the ring formoving the pistons inwardly. Also, since the ring is assembled by merelysliding it over the outer side of the housing, it is easily secured andreleased to obtain access to the pistons.

In accordance with a still further novel aspect of the invention, eachrigid insert includes a rib having opposite sides which lie in planes ofleast strain in the deformable material of the annulus as the annulusis'constricted, whereby the tendency for the bond between the rigidinserts and the annulus to bebroken is reduced. More .particularly, aplane bisecting each rib is skewed with respect to' radial planesthrough the axis of the annulus to an extent dependent upon the plane ofleast strain.

In the drawings, wherein like reference characters are used to designatelike parts:

FIG. 1 is a perspective view of an annular blowout preventer constructedin accordance with the present invention, as seen from the top and sidethereof, and with a portion removed to show a pipe within the bore ofthe 'packer in its unconstricted position;

FIG. 2 is a vertical sectional view through the blowout preventer ofFIG. 1, as seen along broken line 2-2 of FIG. 1;

FIG. 3 is a partial top plan view of the packer of the preventer ofFIGS. 1 and 2, in its unconstricted position, and showing in brokenlines the ribs of its rigid inserts;

FIG. 4 is a vertical sectional view through the packer as seen alongbroken line 4-4 of FIG. 3;

FIGS. 4A and 4B are sectional views of other forms of protuberances atthe end of the packer;

FIG. 5 is a cross-sectional view, on an enlarged scale and as seen alongbroken line 5--5 of FIG. 2, of a connection between adjacent packerconstricting parts which synchronizes their radial movement;

FIG. 6 is a partial vertical sectional view of the preventer, similar toFIG. 2, but showing the packer upon constriction inwardly to seal aboutthe pipe in the bore of the housing;

FIG. 7 is another partial sectional view similar to FIG. 6, but showingthe packer in a further constricted position to close an open hole inthe bore of the preventer housing;

FIG. 8 is a perspective view of a rigid insert;

FIG. 9 is a horizontal sectional view of the insert, as seen alongbroken line 9-9 of FIG. 8; and

FIG. 10 is a diagrammatic illustration of the manner in which theorientation of the rib of the rigid insert within the packer may bedetermined in order to arrange its opposite sides generally in planes ofleast strain.

With reference now to the details of the above-described drawings, thepreventer, which is designated in its entirety by reference character20, includes a housing 21 which is annular in shape and has acylindrical bore 22 extending axially through it. Threaded holes 23 andring grooves 24 are pro vided at both ends of the housing for coaxialconnection and sealing to other wellhead members (not shown).

With the preventer 20 thus connected as a part of the wellhead, a drillpipe P forming part of the drill string'may extend through its bore 22and into the well bore. Alternatively, a Kelly or other out of-roundmember may extend through the bore 22 of the blowout preventer. Stillfurther, the bore may. be empty so as toform an open hole therethrough.As,

known in this art, there may be occasion for the preventer to be used insealing about the member in the hole, such as the pipe P or the Kelly,so as to close off the annular space between such member and the bore22, or alternatively to seal off with itself so as to close an openhole.

Housing 21 is made up of a body which is generally L- shaped invertical, half cross section to provide an upwardly opening shelf aboutits interior, and a cap 26 disposable over the upper end of the body 25to form an annular recess 27 about bore 22. Cap 26 has a bore 22atherethrough which fonns a continuation of a bore 22b through the lowerend of body 25, the two bores thus fonning the bore 22 through thehousing. Body 25 includes a bridging ring 40 (to be described below),and cap 26 and the top surface of the ring fonn the upper and lower ends27a and 27b respectively, of the recess. The outer wall of recess 27 isconcentric with bore 22 of the housing, and the ends 27a and 27b of therecess are perpendicular to its axis.

Cap 26 is secured to the upper end of the body 25 by a series of capscrews 28 extending through holes in the cap for connection withthreaded holes 29 in the body 25. Threaded holes 30 in cap 26 mayreceive eyes for lifting it into and out of place. An O-ring 31 about areduced lower end portion of the cap seals with respect to an innerannular wall 32 of the body 25 above the recess 27.

A packer 33 is disposed within the recess 27 of the preventer housing 21for movement between an unconstricted position in which its bore 35 issubstantially axially aligned with the housing bore 22, as best shown inFIGS. 1 and 2, and a constricted position in which its bore 35 is movedradially inwardly into the housing bore for sealing about the pipe P, asbest shown in FIG. 6, or for sealing upon itself when the bore is empty,as best shown in FIG. 7. As will be described below, the packer is somoved by means of constricting parts including laterally extendingsegments 36 disposed about the outer side of the packer within recess 27and adapted to be moved radially inwardly and outwardly by means of thehydraulically operated pistons.

Packer 33 is cylindrical in shape, with its outer side and bore 35concentric, and its ends 37 and 38 perpendicular to the axis of the bore35. It fits closely within the upper and lower ends 27a and 27b of therecess and, as best shown in FIG. 2, when the packer is unconstricted,segments 36 are disposed with their inner arcuate faces adjacent itsouter side and their outer arcuate faces adjacent the outer side of therecess 27. Bore 22b of the housing is connected to the radially outerportion of the recess 27 behind the outer side of the packer by a seriesof slots 39 formed in the bridging ring 40 to permit well pressure toact over the outer side of the packer.

The constricting segments 36 are circumferentially spaced to permit themto move radially inwardly to constrict the packer. As will be apparentfrom FIG. 5, they are caused to move in unison by means of pins 60connecting the opposite ends of adjacent segments. Thus, one end of eachpin is threadedly received in a socket 61 in one segment, while itsother end is slidably received in a socket 62 in an adjacent segment.Each segment is so moved by means of a piston 63 having a seal ring 69slidable within a cylinder 64 extending inwardly from the outer side ofbody 25 of housing 21. Each piston is connected to a segment 36 by a rod66 having a stud 65 threadedly connected between a socket on the innerend of the rod and a central hole in the segment. Each rod 66 extendsthrough a seal such as an O-ring 67 carried within an opening 68 throughthe housing 25 between the recess 27 and a cylinder 64.

Upon removal of the cap 26 from the body 25 of the housing, the packer33 may be lifted from or lowered into the recess 27. With the packerremoved from the recess, access may be had to the segments 36 forreplacing or repairing them. Thus, the threaded connection of each stud65 to the piston rod enables the rod to be disconnected from the stud,so that the segment may be withdrawn and removed from its operatingposition within the recess 27.

The outer ends of cylinders 64 are closed by means of a ring 70 whichsurrounds body 25 and is seated on a shoulder 71.

This ring is normally prevented from moving upwardly by a pin 70aremovably connected to cap 26. However, when the pin is removed, thering may be lifted from and lowered into position for closing thecylinders 64. When lifted, the ring 70 permits access to any one or allof the pistons 63 for replacing or repairing them. Due to the threadedconnection of the piston rod 66 to the stud 65, the piston may berotated so as to release it from the stud 65 and permit it to bewithdrawn from its cylinder 64.

Seal rings 72 and 73 about body 25 above and below cylinders 64 sealwith respect to ring 70 to form an annular space about pistons 63 intowhich pressure fluid may be introduced through a conduit 74 connectingwith a passageway 75 leading thereto. This pressure fluid urges thepistons inwardly and thus the packer to a constricted position.

Alternatively, pressure fluid may be introduced into cylinders 64 on theinner side of pistons 63 to urge them outwardly and permit the packer toexpand. This fluid is introduced through a conduit 75a connecting withan annular passageway 76 which is formed from the lower side of the body25 and then covered by a ring 77 welded to the body. Individualpassageways 78 then connect passageway 76 with the inner end of eachcylinder 64.

Packer 33 includes a massive annulus 34 of rubberlike material havingits bore 35 formed therethrough and a circular series of rigid inserts41 which extend through the annulus from one end to the other. Eachsurface insert is bonded to the annulus and includes a rib 42 having aflange 43 at each end which overhangs the rib on all sides, as bestshown in FIGS. 8 and 9. The ribs are disposed generally midway betweenthe bore 35 and the outer side of the annulus, while the flanges aredisposed with their innennost edges 43a flush with the bore when theannulus is unconstricted.

The outermost edges 43b of the flanges 43 of the ribs of the packerillustrated in all but FIGS. 4A and 4B are disposed inwardly of theouter side of the annulus to leave an annular portion at each end of theannulus surrounding the flanges. Each annular portion protrudes at 44beyond the adjacent end surface of the flange 43 for engaging theopposite end surface of recess 27. Inward movement of the segments 36constricts the packer, urging the top protuberance upwardly against theupper end of the recess to supplement the action of well pressure on thelower end of the packer.

In the packer modification illustrated in FIG. 4A, an annular surface44a protrudes from an annular portion of the packer annulus intermediatethe inner and outer edges of the flanges. Thus, this annular portion isreceived within grooves 44b across the outer sides of the flanges. Inthe other packer modification illustrated in FIG. 48, an annular surface440 protrudes from an annular portion of the annulus received withingrooves 44d formed in the rear outer comers of the flanges. As in thecase of the surface 44, each of the protruding surfaces 44a and 440 onthe upper end of the packer are urged upwardly against the upper end ofthe recess 27 as the packer is constricted.

Although the protruding surfaces on the lower end of the annulus mayalso form a seal against the lower end 27b of the recess, the lowerportion 22b of the bore is nevertheless connected through slots 39 tothe recess behind the annulus. Thus, well pressure will still haveaccess to the recess 27 behind the outer wall of the annulus. Since theprotruding surface on the upper end of the annulus seals with respect tothe upper end 270 of the recess, the differential between this wellpressure and atmospheric pressure in the upper portion 22a of the boreis effective over a substantial portion of the height of the packer tosupplement the force of the actuators of the segments 36 in maintainingthe annulus in its constricted position.

Inasmuch as the packer is symmetrical end-for-end, it may be disposed inthe recess 27 of the housing with either end up. Thus, if an upperprotruding surface is damaged, the packer may be inverted to dispose theeffective lip at its upper end.

As the packer is constricted, the rigid inserts 41 are also caused tomove inwardly, although to a lesser extent than the annulus itself. Thatis, as will be appreciated from a comparison of FlGS. ii and 2 withFIGS. 6 and 7, upon constriction of the packer, the verticallymidportion of its bore 35 will move radially inwardly past the innermostedges 43a of the flanges 43 of the inserts. As the rigid inserts moveinwardly, these innermost edges of the flanges move into the bore 22 ofthe housing to overhang a substantial portion of the annulus which hasmoved into the bore" 22, thereby reducing the likelihood of extrusion ofthe annulus past the flanges.

Flanges 43 of the inserts are arranged radially with respect to the axisof the annulus so that'each flange has outwardly diverging sides and isbisected by a radius of the annulus. As seen in FIGS. 3 and 4, theopposite sides of the flanges 43 are spaced apart with no rubber betweenthem in the unconstricted position of the packer to permit the sides ofthe flanges to move circurnferentially toward one another as the flangesmove radially inwardly.

The opposite sides of the rib 42 of each insert are parallel to oneanother and disposed angularly with respect to radii of the annulusintersecting such sides, and thus angularly with respect to the radialvertical plane bisecting the flanges at each end of the rib. Moreparticularly, the opposite sides of rib 42 are disposed approximatelywithin planes of least strain of the rubber of the annulus duringmovement of the annulus from unconstricted to constricted positions, soas to reduce the likelihood of breaking the bond between the ribs andthe annulus, with consequent reduction of its efiective life.

An approximation of the angles which such planes make with a radius ofthe annulus may be easily determined for particular cases by thoseskilled in the art, and FlG. 10 illustrates a method for doing so. Thus,since constriction of the annulus causes the innermost portions thereofto move inwardly a greater distance than the outermost portions thereof,the intermediate area of the annulus surrounding each rib 42 is causedto change shape during constriction. For example, as shown in FIG. 10, acircular area A of the annulus, having a diameter equal to the length ofrib 42 in its unconstricted position, is changed to a somewhategg-shaped area B when constricted.

Although the shape of this area has changed, there are nevertheless twodiameters of area A which remain constant in length duringtransformation to area B. Either of these diameters defines anapproximate vertical plane of least strain.

Obviously, the location of these planes of least strain and thus thearrangement of the ribs will be dependent upon the extent to which theannulus is to be constricted in use. However, in practice, it ispossible to design forplanes of least strain in the predominant use ofthe preventer, which may for example ,be for sealing about a drill pipeof given size. It has been found that excellent results are obtained bydisposing the sides of the rib at an angle of about 45 to the radiusbisecting such sides.

From the foregoing it will be seen that this invention is one welladapted to attain all of the ends and objects hereinabove set forth,together with other advantages which are obvious and which are inherentto the apparatus.

it will be understood that certain features and subcombinations are ofutility and may be employedwith reference to other features andsubcombinations. This is contemplated by and is within the scope of theclaims.

As many possible embodiments may be made of the invention withoutdeparting from the scope thereof, it is to be understood that all matterherein set forth or shown in the accompanying drawings is to beinterpreted as illustrative and not in a limiting sense.

lclaim:

l. A packer for disposal within a recess in the bore of the housing ofan annular blowout preventer, comprising an annulus of deformablematerial, and a substantially circular series of rigid,circurnferentially relatively movable inserts including ribs extendingthrough the annulus from one end to theother, and flanges on the ends ofthe ribs on at-least one end of the annulus, said annulus having anannular surface at said one end which is substantially coplanar with theend surfaces of said flanges for sealing against an oppositely facingend surface of the housing recess and the outer side of said annulusbeing radially constrictible.

2. A packer of the character defined in claim 1, wherein said annularsealing surface is adjacent the outer side of said annulus.

3. A packer of the character defined in claim 1, wherein said annularsealing surface protrudes beyond the end surfaces of the flanges at saidone end of the annulus.

4. A packer of the character defined in claim 1, wherein there areflanges on both ends of the rib, and there is a sealing surface on eachend of the annulus, so that the packer may be disposed with either endfor sealing against said end surface of the housing recess.

5. A packer for disposal within the housing of an annular blowoutpreventer, comprising an annulus of resilient material having a boreextending axially therethrough and an outer, radially constrictible sideconcentric with the bore, and a substantially circular series of rigid,circurnferentially relatively movable inserts extending through theannulus from one end surface to the other, each said insert including arib having a flange extending laterally thereof at each end, each flangehaving a radially outermost surface which is spaced inwardly of theouter side of the annulus, and the portion of said annulus whichsurrounds the outermost surfaces of the flanges at each end of theannulus having a surface which is substantially coplanar with theadjacent end surfaces of said flanges for sealing against an oppositelyfacing surface of the housing.

6. A packer of the character defined in claim 5, wherein each saidsealing surface protrudes beyond the adjacent end surfaces of theflanges.

7. An annular blowout preventer, comprising a housing having a boretherethrough and an annular recess extending outwardly from the bore, apacker comprising an annulus of resilient material within the recess andhaving a bore therethrough substantially axially aligned with the borethrough the housing, and a substantially circular series of rigid,circurnferentially relatively movable inserts in the annulus, one end ofthe annulus having an annular surface for engaging the oppositely facingend of the recess, and radially reciprocable actuators within the recessand in circumferentially noncontinuous sealing engagement about theouter side of the annulus for constricting the annulus and for urgingsaid annular surface into tight sealing engagement with said end of therecess, the inner edges of the ends of said rigid in serts entering thebore of said housing as the annulus is so constricted.

8. A blowout preventer of the character defined in claim 7, wherein theannulus has an annular surface at each end for engaging the end of therecess regardless of which end is up.

9. A blowout preventer of the character defined in claim 7, wherein saidactuators include circurnferentially separated, laterally extendingsegments having inner arcuate surfaces for substantially surrounding theouter side of the annulus within the recess, and pistons reciprocablewithin the housing for moving the segments inwardly and outwardly.

10. A packer for use in an annular blowout preventer, comprising anannulus of deformable material, and a substantially circular series ofrigid inserts bonded to the annulus, each insert including a rib havingopposite sides which lie generally within planes of least strain in saidmaterial as the annulus is radially constricted.

11. A packer of the character defined in claim 10, wherein each insertalso includes a flange overhanging the rib at each end of the annulus.

12. A packer for use in an annular blowout preventer, comprising anannulus of deformable material, and a substantially circular series ofrigid inserts bonded to the annulus, each said insert including a ribhaving flat sides disposed at acute angles to any radii of the annulusintersecting said sides and lying generally within planes of leaststrain in said material as the outer diameter of said annulus isradially constricted.

13. A packer of the character defined in claim 12, wherein each insertalso includes a flange overhanging the rib at each end of the annulus.

14. An annular blowout preventer, comprising a housing having a boretherethrough an an annular recess extending outwardly from the bore, apacker comprising an annulus of resilient material within the recess andhaving a bore therethrough substantially axially aligned with the borethrough the housing, and a substantially circular series of rigidinserts bonded to the annulus, each said insert including a rib havingits opposite sides lying generally within planes of least strain in saiddeformable material as the annulus is radially constricted.

15. An annular blowout preventer of the character defined in claim 14,wherein the inner edge of each end of each said insert moves into thebore of the housing upon constriction of the annulus.

16. An annular blowout preventer, comprising a housing having a boretherethrough and an annular recess extending outwardly from the bore, apacker comprising an annulus of resilient material within the recess andhaving a bore therethrough substantially axially aligned with the borethrough the housing, and a substantially circular series of rigidinserts bonded to the annulus, each said insert including a rib havingsides disposed at acute angles to radii of the annulus intersecting saidsides and lying generally within planes of least strain in said materialas the outer diameter of said annulus is radially constricted.

17. An annular blowout preventer of the character defined in claim 16,wherein the inner edge of each end of each said insert moves into thebore of the housing upon constriction of the annulus.

18. A rigid insert for the packer of an annular blowout preventer,comprising a rib having flat, parallel sides, and a flange at each endof the rib which overhangs the rib on all sides, the rib having sidesextending at acute angles with respect to a plane bisecting the flangesand lying generally within planes of least strain in the resilientmaterial of said packer when the insert is arranged within and bonded tosaid material to dispose its flanges at opposite ends of the packer anddispose said bisecting plane generally coincident with a radius of thepacker.

19. An annular blowout preventer. comprising a housing having a boretherethrough and an annular recess about the bore, an annular packerwithin the recess, a series of cylinders extending into the housing fromits outer side, a piston sealably slidable within each cylinder, packerconstricting segments within the housing recess about the outer side ofthe packer, rods extending sealably within the housing to connect eachsegment with a piston, a fluid connection with each cylinder on theinner side of the piston therein, a ring disposable about the outer sideof the housing to cover the outer ends of the cylinders, means sealingbetween said outer side of the housing and the ring to form an annularspace communicating with the outer end of each piston, and a fluidconnection to the space.

20. An annular blowout preventer, comprising a housing having a boretherethrough an an annular recess extending outwardly from the bore, apacker comprising an annulus of resilient material within the recess andhaving a bore therethrough substantially axially aligned with the borethrough the housing, and a substantially circular series of rigid,circumferentially relatively movable inserts in the annulus, one end ofthe annulus having an annular surface for engaging the oppositely facingend of the recess, radially reciprocable actuators within the recess andin circumferentially noncontinuous sealing engagement about the outerside of the annulus for constricting the annulus and for urging saidannular surface into tight sealing engagement with said end of therecess, the inner edges of the ends of said rigid inserts entering thebore of said housing as the annulus is so constricted, and means foradmitting fluid from the end of the bore which connects with the otherend of the recess to the outer side of the annulus within said recess.

1. A packer for disposal within a recess in the bore of the housing ofan annular blowout preventer, comprising an annulus of deformablematerial, and a substantially circular series of rigid,circumferentially relatively movable inserts including ribs extendingthrough the annulus from one end to the other, and flanges on the endsof the ribs on at least one end of the annulus, said annulus having anannular surface at said one end which is substantially coplanar with theend surfaces of said flanges for sealing against an oppositely facingend surface of the housing recess and the outer side of said annulusbeing radially constrictible.
 2. A packer of the character defined inclaim 1, wherein said annular sealing surface is adjacent the outer sideof said annulus.
 3. A packer of the character defined in claim 1,wherein said annular sealing surface protrudes beyond the end surfacesof the flanges at said one end of the annulus.
 4. A packer of thecharacter defined in claim 1, wherein there are flanges on both ends ofthe rib, and there is a sealing surface on each end of the annulus, sothat the packer may be disposed with either end for sealing against saidend surface of the housing recess.
 5. A packer for disposal within thehousing of an annular blowout preventer, comprising an annulus ofresilient material having a bore extending axially therethrough and anouter, radially constrictible side concentric with the bore, and asubstantially circular series of rigid, circumferentially relativelymovable inserts extending through the annulus from one end surface tothe other, each said insert including a riB having a flange extendinglaterally thereof at each end, each flange having a radially outermostsurface which is spaced inwardly of the outer side of the annulus, andthe portion of said annulus which surrounds the outermost surfaces ofthe flanges at each end of the annulus having a surface which issubstantially coplanar with the adjacent end surfaces of said flangesfor sealing against an oppositely facing surface of the housing.
 6. Apacker of the character defined in claim 5, wherein each said sealingsurface protrudes beyond the adjacent end surfaces of the flanges.
 7. Anannular blowout preventer, comprising a housing having a boretherethrough and an annular recess extending outwardly from the bore, apacker comprising an annulus of resilient material within the recess andhaving a bore therethrough substantially axially aligned with the borethrough the housing, and a substantially circular series of rigid,circumferentially relatively movable inserts in the annulus, one end ofthe annulus having an annular surface for engaging the oppositely facingend of the recess, and radially reciprocable actuators within the recessand in circumferentially noncontinuous sealing engagement about theouter side of the annulus for constricting the annulus and for urgingsaid annular surface into tight sealing engagement with said end of therecess, the inner edges of the ends of said rigid inserts entering thebore of said housing as the annulus is so constricted.
 8. A blowoutpreventer of the character defined in claim 7, wherein the annulus hasan annular surface at each end for engaging the end of the recessregardless of which end is up.
 9. A blowout preventer of the characterdefined in claim 7, wherein said actuators include circumferentiallyseparated, laterally extending segments having inner arcuate surfacesfor substantially surrounding the outer side of the annulus within therecess, and pistons reciprocable within the housing for moving thesegments inwardly and outwardly.
 10. A packer for use in an annularblowout preventer, comprising an annulus of deformable material, and asubstantially circular series of rigid inserts bonded to the annulus,each insert including a rib having opposite sides which lie generallywithin planes of least strain in said material as the annulus isradially constricted.
 11. A packer of the character defined in claim 10,wherein each insert also includes a flange overhanging the rib at eachend of the annulus.
 12. A packer for use in an annular blowoutpreventer, comprising an annulus of deformable material, and asubstantially circular series of rigid inserts bonded to the annulus,each said insert including a rib having flat sides disposed at acuteangles to any radii of the annulus intersecting said sides and lyinggenerally within planes of least strain in said material as the outerdiameter of said annulus is radially constricted.
 13. A packer of thecharacter defined in claim 12, wherein each insert also includes aflange overhanging the rib at each end of the annulus.
 14. An annularblowout preventer, comprising a housing having a bore therethrough an anannular recess extending outwardly from the bore, a packer comprising anannulus of resilient material within the recess and having a boretherethrough substantially axially aligned with the bore through thehousing, and a substantially circular series of rigid inserts bonded tothe annulus, each said insert including a rib having its opposite sideslying generally within planes of least strain in said deformablematerial as the annulus is radially constricted.
 15. An annular blowoutpreventer of the character defined in claim 14, wherein the inner edgeof each end of each said insert moves into the bore of the housing uponconstriction of the annulus.
 16. An annular blowout preventer,comprising a housing having a bore therethrough and an annular recessextending outwardly from the bore, a packer comprising an annulus ofresilient material within the recess and having a bore therethroughsubstantially axially aligned with the bore through the housing, and asubstantially circular series of rigid inserts bonded to the annulus,each said insert including a rib having sides disposed at acute anglesto radii of the annulus intersecting said sides and lying generallywithin planes of least strain in said material as the outer diameter ofsaid annulus is radially constricted.
 17. An annular blowout preventerof the character defined in claim 16, wherein the inner edge of each endof each said insert moves into the bore of the housing upon constrictionof the annulus.
 18. A rigid insert for the packer of an annular blowoutpreventer, comprising a rib having flat, parallel sides, and a flange ateach end of the rib which overhangs the rib on all sides, the rib havingsides extending at acute angles with respect to a plane bisecting theflanges and lying generally within planes of least strain in theresilient material of said packer when the insert is arranged within andbonded to said material to dispose its flanges at opposite ends of thepacker and dispose said bisecting plane generally coincident with aradius of the packer.
 19. An annular blowout preventer, comprising ahousing having a bore therethrough and an annular recess about the bore,an annular packer within the recess, a series of cylinders extendinginto the housing from its outer side, a piston sealably slidable withineach cylinder, packer constricting segments within the housing recessabout the outer side of the packer, rods extending sealably within thehousing to connect each segment with a piston, a fluid connection witheach cylinder on the inner side of the piston therein, a ring disposableabout the outer side of the housing to cover the outer ends of thecylinders, means sealing between said outer side of the housing and thering to form an annular space communicating with the outer end of eachpiston, and a fluid connection to the space.
 20. An annular blowoutpreventer, comprising a housing having a bore therethrough an an annularrecess extending outwardly from the bore, a packer comprising an annulusof resilient material within the recess and having a bore therethroughsubstantially axially aligned with the bore through the housing, and asubstantially circular series of rigid, circumferentially relativelymovable inserts in the annulus, one end of the annulus having an annularsurface for engaging the oppositely facing end of the recess, radiallyreciprocable actuators within the recess and in circumferentiallynoncontinuous sealing engagement about the outer side of the annulus forconstricting the annulus and for urging said annular surface into tightsealing engagement with said end of the recess, the inner edges of theends of said rigid inserts entering the bore of said housing as theannulus is so constricted, and means for admitting fluid from the end ofthe bore which connects with the other end of the recess to the outerside of the annulus within said recess.